Combustion unit



1946 Q. F. HEATH f fi p COMBUSTION UNIT Filed June 22, 1944 Fig. 4.

4 Fig. 5.

27 M li Invent or Charles F Heath b W His Attorney.

Patented July 9, 1946 COMBUSTION UNIT Charles F. Heath, Schenectady, N.Y., assignor to General Electric Company, a corporation of New YorkApplication June 22, 1944, Serial No. 541,605

5 Claims. 1

The present invention relates to combustion units such as are used inconnection with gas turbine power plants for supplying hot gases to theturbine wheel, and especially to such combustion units which compriseinner and outer tubular casings spaced to provide an annular chamber towhich air for combustion is supplied and from which chamber the airflows through openings to the interior of the inner casing, Suchcombustion units ordinarily utilize an ignition plug for startingcombustion.

My invention relates more particularly to the ignition plug for such acombustion unit and has for its object to provide an improved ignitionplug arrangement which is simple in structure, easily installed andwhich can be readily removed and replaced.

For a consideration of what I believe to be novel and my invention,attention is directed to the following specification and to the claimsappended thereto.

In the drawing:

Fig. 1 is a sectional view of a part of a combustion unit provided withan ignition plug structure embodying my invention; Fig. 2 is a top planview of one of the members of the ignition plug; Fig. 3 is a detail viewtaken on line 3-3, Fig. 2, and Fig. 4 is a detail vew of a connector.

Referring to the drawing, l indicates the outer casing and 2 indicatesthe inner casing of a combustion unit. Casings l' and 2 are held inspaced relation to each other by suitable spacers, one of which isindicated at 3 to provide an annular air chamber 4. Air is supplied toair chamber 4 through a conduit 5 and from chamber 4 it passes throughsuitable openings to the interior of casing 2 where combustion takesplace. A fuel nozzle for supplying fuel to the combustion unit isindicated at 6. The construction so far described is shown only by wayof example and is to be taken as typical of any suitable double walledcombustion unit construction.

The ignition plug comprises an insulator member 1 supported in anopening in inner casing 2 and an insulator member 8 supported in anopening in outer casing I. Insulator member 1 is arranged so that it maybe readily attached to and removed from casing 2. To this end, there isprovided in the opening in casing 2 an insulator holder comprising ametal ring 9 which may be welded to casing 2 and is provided with aninwardly projecting shoulder l and, spaced from such shoulder, a seriesof inwardly projecting ears ll. Ears ll may be carried by a ring l2which is suitably welded in position. The insulator member I is providedon its periphery with a series of circumferentially spaced ears l3 whichare adapted to engage under ears H. Thus, the insulator member may beinserted into the holder by passing the ears l3 between adjacent ears Hand turning the insulator to bring the ears l3 under the ears ll. Thusears 13 are clamped between ears H and shoulder I0. Extending throughinsulator member 1 is a metal post l4, the inner end of which forms anelectrode terminal I5. Adjacent electrode terminal [5 is a secondelectrode terminal l6 which is suitably fastened to the side of theinsulator as is indicated at H in Fig. 3. Thus, when the insulatormember 1 is in place in its holder, electrode terminal I6 is grounded onthe metal ring 9. Attached to the outer end or post I4 is a flexibleconductor rod or connector l8 which may be attached to the post in anysuitable way and which is provided with an angularly turned end l9 toform a stop. In the present instance, post I4 is shown as being held inposition by a nut threaded onto its outer end and the end of rod 18 isfastened in an opening through the nut and post. In insulator member Iare a plurality of tangentially arranged openings 20 through which airis supplied to a recess 2l' in the insulator member 1 to provide a swirlof air around the parts to cool the parts, particularly the electrodepoints, effect an improved distribution of combustible gases withrespect to the points, and prevent the deposition of carbon particles orother foreign matter on the insulator member. Thus when starting up, airwill flow through openings 20 to scour the .pocelain surfaces of carbonparticles which may have become deposited thereon but at the same timesuch swirl of air will not prevent combustible mixture from reaching theignition points.

Insulator member 8 is carried by a suitable metallic holder 22 which isattached by a ring of studs 23 to a ring 24 which is suitably attachedto the edge of the opening in casing l. Gaskets between the severalparts are indicated at 25. Extending through insulator member 8 is ametal post 26 which on its inner end is provided with a head 21 whichtakes against insulator member 8 on the one side and on its outer endwith a head 28 which takes against the insulator member 8 on the otherside. Connected to head 28 is .a suitable connector 29 to which anignition wire 30 is connected. Head 21, as shown particularly in Fig. 4,is provided with a recess 3! adapted to fit over the connector rod l8 toform an electrical connection between post 26 and post l4. Rod I8 hassome flexibility and the arrangement is such that head 21 presses downon the rod, thus putting the rod under tension to form a good electricalconnection. At the same time rod l8 can slide through the head. Thisarrangement permits the inner and outer casings I and 2 to expand andcontract relatively to each other without affecting adversely theelectrical connection or putting a strain on any of the parts. In otherwords, rod I8 forms a yieldable connection between the two ignition plugmembers. In this connection, it will be understood that combustion unitsof this type operate at relatively high temperatures and that there maybe considerable relative expansion between the two casing members.

It will be noted that in the present instance,

the opening in the inner casing 2 is out of line,

with the opening in the outer casing l. The opening in the inner casing2 is positioned at a point in the casing to provide for the mostadvantageous ignition. The opening in the outer casing I is larger thanthe opening in the inner casing 2. By removing the studs 23, theinsulator member 8 may be removed from its position in the opening incasing l. Upon being removed, the head 21 is lifted away from engagementwith the connector rod Ill. The insulator member I may be removedthrough the opening in the casing I, it being necessary merely to reachthrough the opening, turn the insulator member I to bring ears l3 fromunder the ears H and lift the insulator member out. With thisarrangement, it will be seen that the insulator member 1 can be quicklyand easily removed for clean ing or replacement. While in the presentinstance, the two insulator members 1 and 8 are shown as being out ofalignment, they may in some instances be mounted in alignment, if founddesirable.

In operation, the air in the annular air chamber 4 is at somewhat higherpressure than that which obtains inside casing 2. This difference inpressure causes a continuous flow of air through the tangential openings20 into the re cess 2|. This sets up a swirl of air around recess 2| andaround the ignition points, the ignition points being at the center ofthe swirl. As pointed out above, this serves to cool the ignition plugparts and keep the insulator parts scoured free from deposits of carbonor other foreign matter. At the same time, since the ignition points aresomewhat below and at the center of the swirl of air, the swirl of airdoes not prevent combustible mixture from reaching the ignition points.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof,but I desire to have it understood that the apparatus shown. is onlyillustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a combustion unit, spaced inner and outer casings, each providedwith an opening, the opening in the outer casing being out of alignmentwith the opening in the inner casing, an ignition plug member mounted inthe opening in the inner casing having a post extending through it, theinner end of which forms an electrode terminal, an ignition plug membermounted in the opening in the outer casing and having a conducting postextending through it, a flexible rod connected to one of said posts andbiased toward the other post by reason of its flexibility, and meansforming a sliding connection between the flexible rod and said otherpost for electrically connecting the posts together.

2. In a combustion unit, spaced inner and outer casings, each providedwith an opening, the

opening in the inner casing being out of alignment with the opening inthe outer casing, an ignition plug member removably mounted in theopening in the inner casing having a post extending through it, theinner end of which forms an electrode terminal, an ignition plug membermounted in the opening in the outer casing and having a conducting postextending through it, and a flexible rod connected to the first-namedpost and extending across the inner side of the plug member mounted inthe outer casing, the flexibility of the rod biasing it outwardly towardsuch plug member, the second-named post having at its inner end a headprovided with a slot which fits over said flexible rod whereby theflexible rod is yieldably and slidably connected with said second-namedpost.

3. In a combustion unit, spaced inner and outer casings, each providedwith an opening, said openings being out of alignment with each other,an ignition plug mounted in the opening in the inner casing having apost extending through it, the inner end of which forms an electrodeterminal, an ignition plug member mounted in the opening in the outercasing and having a conducting post extending through it, a yieldableconductor rod connected at one end to the outer end of the first-namedpost and having a free end which extends to a position in line with theopening in the outer casing and biased toward said opening by reason ofits inherent resiliency, the inner end of the conducting post carried bythe outer casing having a head which is pressed into engagement withsaid rod at a point short of the end of the rod to make slidingengagement with the rod.

4. In a combustion unit, spaced inner and outer casings, each providedwith an opening, said openings being out of alignment with each other,an ignition plug mounted in the opening in the inner casing having apost extending through it, the inner end of which forms an electrodeterminal, an ignition plug member mounted in the opening in the outercasing and having a conducting post extending through it, a yieldableconductor rod connected at one end to the outer end of the first-namedpost and having a free end which extends to a position in line with theopening in the outer casing and biased toward said opening by reason ofits inherent resiliency, the inner end of the conduct ing post carriedby the outer casing having a head which is pressed into engagement withsaid rod at a point short of the end of the rod to make slidingengagement with the rod, the opening in the outer casing being largerthan the first-named ignition plug whereby it may be inserted andremoved through such opening.

5. The combination with a combustion chamber having spaced inner andouter walls which define an air chamber from which air flows to theinterior of the inner wall, of an ignition plug member mounted in anopening in the inner wall comprising an insulator, electrode points onthe inner side of the insulator, walls of the insulator being shaped todefine an angularly extending annular recess extending rearwardly of theelectrode points, and tangential passages which extend through theinsulator and communicate with said recess through which air flows fromsaid air chamber to provide a swirl of air around the electrode points.

CHARLES F. HEATH.

